The discovery of an early stage of Alzheimer's disease may drive up the number of Americans thought to have the memory-robbing disorder by 100 percent or more, researchers at Chicago's Rush University reported Monday in the science journal Neurology.
Mild cognitive impairment, in which a person has increasing difficulty forming new memories, had been considered a normal part of aging but now appears to be an indicator of Alzheimer's disease, said the study's lead author, Dr. David A. Bennett, director of the Alzheimer's Disease Center at Rush.
The researchers emphasized, however, that most people who worry about losing their memory as they age are not suffering from creeping Alzheimer's.
The findings emerged from the largest study ever conducted on people diagnosed with mild cognitive impairment.
The research, which involved postmortem examinations of the brains of 180 Catholic nuns, priests and brothers, indicates that most of the 2.5 million to 10 million Americans with that condition may already have some degree of Alzheimer's disease.
The disease is known to affect one in 10 people over age 65 and nearly half of those over 85, figures that could increase substantially if the early stage is added to the calculations.